/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.method.annotation;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.WebAsyncTask;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;

/**
 * Handles return values of type {@link WebAsyncTask}.
 *
 * @author Rossen Stoyanchev
 * @since 3.2
 */
public class AsyncTaskMethodReturnValueHandler implements HandlerMethodReturnValueHandler {

    @Nullable
    private final BeanFactory beanFactory;


    public AsyncTaskMethodReturnValueHandler(@Nullable BeanFactory beanFactory) {
        this.beanFactory = beanFactory;
    }


    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        return WebAsyncTask.class.isAssignableFrom(returnType.getParameterType());
    }

    @Override
    public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
            ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {

        if (returnValue == null) {
            mavContainer.setRequestHandled(true);
            return;
        }

        WebAsyncTask<?> webAsyncTask = (WebAsyncTask<?>) returnValue;
        if (this.beanFactory != null) {
            webAsyncTask.setBeanFactory(this.beanFactory);
        }
        WebAsyncUtils.getAsyncManager(webRequest).startCallableProcessing(webAsyncTask, mavContainer);
    }

}
